Optical scanners operate by imaging an object (e.g. a document) with a light source, and sensing a resultant light signal with an optical sensor array. Each optical sensor or photoreceptor in the array generates a data signal representative of the intensity of light impinged thereon for a corresponding portion of the imaged object. The data signals from the array sensors are then processed (typically digitized) and stored in a temporary memory such as a semiconductor memory or on a hard disk of a computer, for example, for subsequent manipulation and printing or display, such as on a computer monitor. The image of the scanned object is projected onto the optical photosensor array incrementally by use of a moving scan line. The moving scan line is produced either by moving the document with respect to a scanner optical assembly, or by moving the scanner optical assembly relative to the document. Either or both of these methods may be embodied in a flat bed scanner, multi-function printer, or any scanner having manual and automatic feed capabilities.
Various types of photosensor devices may be used in optical scanners. For example, a commonly used photosensor device is the charge coupled device (CCD). A CCD builds up an electrical charge in response to exposure to light. The size of the electrical charge build up is dependent on the intensity and the duration of the light exposure. In optical scanners, CCD cells are aligned in a linear array. The length of the linear array is typically somewhat less than the length or width of the document scanning region. Each photoreceptor of the CCD has a portion of a scan line image impinged thereon as the scan line sweeps across the scanned object. The charge built up in each of the pixels is measured and discharged at regular “sampling intervals.” In most modern optical scanners, the sampling intervals of the CCD arrays are fixed.
An image of a scan line portion of a document is projected onto the scanner's linear photosensor array by scanner optics. In such CCD scanners, the scanner optics include an imaging lens which typically reduces considerably the size of the projected image from its original size. The scanner optics provide good depth of field in a CCD scanner. However, because the photoreceptors are so small in the CCD device, a fairly strong light source such as a fluorescent lamp is needed to illuminate the scan line image region of the document in order to provide sufficient signal strength at each photoreceptor site.
A second type of scanner is the contact image sensor (CIS) scanner. A CIS scanner includes a contact image sensor having a length that is substantially equal to the width of the scanning region. The photoreceptors in a CIS are substantially the same size as the pixel resolution of the scanner. Because the photoreceptors in the CIS are so much larger than they are in a CCD, a lower power light source (such as one or more LED's) is sufficient to provide enough illumination in the scan line image region. The CIS has a short depth of field and is typically mounted beneath the transparent platen upon which the document is placed. One or more rollers in the CIS carriage are biased against the bottom of the transparent platen so that the CIS is always at substantially the same distance from the top of the transparent platen.
Photoreceptors in a CCD or CIS scanner linear photosensor array are aligned in a “cross” direction, i.e., a direction parallel to the longitudinal axis of the scan line image which is projected thereon. The direction perpendicular to the “cross” direction will be referred to herein as the “scan” direction (i.e., paper or sensor linear array movement direction for scanning of the image).
At any instant when an object is being scanned, each photoreceptor in the photosensor array has a corresponding area on the object which is being imaged thereon. This corresponding area on the scanned object is referred to herein as a pixel. An area on a scanned object corresponding to the entire extent of the linear photosensor array is referred to herein as a scan line. For descriptive purposes, a scanned object is considered to have a series of fixed adjacently positioned scan lines. Further, scanners are typically operated at a scan line sweep rate such that one scan line width is traversed during each sampling interval.
In addition, when working with cut sheet print media, a copying, scanning or multifunction printing apparatus may provide automatic document feed, as well as manual document placement capabilities. An automatic document feeder (ADF) mechanism is capable of automatically loading and unloading single sheets sequentially to a functional station where the apparatus performs an operation, e.g., sequentially scanning the fed document sheets for copying, faxing, displaying on a computer monitor, or the like. Following the operation, the ADF then off-loads a sheet and feeds the immediately following sheet of the document to the functional station. A sequential flow of sheets by the ADF and positioning without the necessity of manual handling reduces the time required to accomplish the complete functional operation. An ADF may be designed to scan single-sided originals or two-sided originals.
Each document fed into the ADF is conveyed to an automatic scanning region where the document is scanned by an image sensor and then the document is conveyed to a point outside the ADF, such as a document output tray. During ADF operation, the image sensor remains fixed at the automatic scanning region “reading” or scanning the image as the document is conveyed past the scanning point by the ADF. During manual scanning, the document lays flat on and covers a portion of the flat platen while the image scanner is moved under the platen the length (or width) of the document to read or scan the document. In many flatbed scanners, the scanning point or portion of the flat platen used to scan a document provided by the ADF is separate and distinct from the portion of the flat platen utilized to scan a document manually positioned on the plate.
Scanners also typically include a lid that covers the transparent platen. In manual document placement operation, the lid is lifted so that the user can place the document on the transparent platen and align it properly. The lid is then closed prior to scanning. For scanners that have an ADF, the bottom of the ADF can function as the lid that covers the transparent platen.
Many scanners or multifunction printers, whether in a home, office, or other public environment, have multiple users, and can optionally be networked. Such a scanner or multifunction printer can store user-preferred default settings, or user-confidential information in its non-volatile storage, e.g. email profiles (username, passwords, and contacts). For a walk-up user who wishes to retrieve user-specific information or settings, the scanner or multifunction printer typically requires the user to login with a password or personal identification number code. However, this requires users to remember yet one more password or PIN number. An alternative is to use biometric scanners such as a thumb scanner or voice recognition to identify the user. However, this would require additional components and hardware costs.
What is needed is a reliable and easy-to-use way to identify users of scanners or multifunction printers without adding significant cost.